Grant: Alliance Grants

Open pit mining of the Athabasca Bituminous Sands in northern Alberta generates considerable volumes of dust. The dusts are dominated by coarse-grained minerals that are largely insoluble such as quartz, but also fine-grained minerals and more reactive phases such as carbonates. The dusts contain varying amounts of trace elements (TEs), some of which may be released to surface waters upon deposition from the air. Some TEs are benign, some are essential micronutrients, but some may be toxic. Peat bog waters which are naturally acidic (pH 4), offer a chance to study the extent to which these dusts dissolve in the peatlands that dominate the landscape. By measuring the concentrations of TEs in bog waters, the chemical reactivity of the dust particles can be judged, and along with it, the bioavailability of TEs. In this sense, peat bogs represent natural biomonitoring systems that can be used to identify the chemical reactivity of atmospheric particles. Sphagnum moss is the dominant plant in bogs, and is typically 90% water by weight. Porewater expressed from Sphagnum will be used to study the reactivity of these particles, as well as water extracted from country foods such as wild berries, and traditional medicinal plants such as the Pitcher Plant (Sarracenia purpurea). Using AF4-ICP-MS (asymmetric flow field flow fractionation coupled to inductively coupled plasma mass spectrometry), size-resolved analyses will allow colloidal forms of TEs (which are not bioavailable) to be distinguished from "truly dissolved", predominantly ionic species (which are bioavailable). Experimental studies in the laboratory using simple organic acids will be used to understand the mechanisms of mineral dissolution, and the influence of complexation reactions on the speciation of TEs. The study will provide new insight into the true environmental impacts of bitumen mining and upgrading.